The present invention provides a separation method of separating (A) and (B), comprising: a step of separating at least either an active hydrogen-containing compound (A) or a compound (B) that reversibly reacts with (A) from a mixture containing (A) and (B) by distillation in a multistage distillation column; and a step of supplying the mixture to an inactive region formed within the multistage distillation column.